I love the story of the man without a "wedding garment" found in Matthew chapter 22. In the story, the king is marrying off his Son and so they invite people from near and far. For an occasion such as this it would be appropriate for people to wear white robes. In fact, the apparel that someone would wear showed the kind of respect they had for the host. Often times a host would supply his guests with the appropriate attire for different reasons. So in this situation the king provided clothing for all of his guests. There was one man who chose not accept the kings clothing, because he felt that his appearance was good enough. Therefore he was not permitted to stay. Some might think this was rude, or inconsiderate of the king. Just like there were requirements for people to be allowed to enter the ceremony, there are requirements to be able to enter into the Kingdom of God. Everyone is invited to come to the kingdom of God, but you have to be willing to accept the requirements. There are a lot of places of businesses that have signs up that say "no shoes, no shirt, no business." Everyone is invited in, but if you aren't wearing any shoes or a shirt they have a right to ask you to leave because you aren't following the requirements they asked you to make in order to be able to enter. The world asks more often then not "what is so 'secret' about the Mormon Temple? If you are so inviting why can't everyone enter at any given time?"
The answer: It is not secret it is sacred. Everyone is invited to enter you just have to be willing to live the requirements that are given to be able to do so. We even wear special clothing in the temple that symbolizes clothing ourselves in covenants, righteousness, and purity in preparation for entering into God’s presence. Choosing not to wear the apparel they ask us to wear is mocking our covenants we have made, rebelling and pretty much admitting to being unclean. The Lord will always accept those who follow him willingly and correctly.